2-benzoyl pyrrole and benzoyl imidazole herbicides

ABSTRACT

Herbicidal compounds have the formula ##STR1## in which R 1  is hydrogen, methyl, ethyl, phenyl, 2-methylphenyl, 3-trifluoromethylphenyl, benzyl, 2-methylbenzyl or vinyl; 
     R 2  is hydrogen, methyl, ethyl or chloro; 
     R 3  is C 1  -C 4  alkyl, C 1  -C 4  alkoxy, C 1  -C 4  haloalkyl, nitro, p-tolyloxy or p-chlorophenoxy; 
     R 4  is hydrogen or a methyl, methoxy, trifluoromethoxy or halo group at the 2, 4- or 5-position; 
     m is --CH or N; and 
     X is O or NOR 5  in which R 5  is methyl or ethyl; provided that: 
     (a) when R 1  is methyl, and 
     (i) R 3  is methyl, then R 4  is 4-methyl, 4-methoxy or chloro; 
     (ii) R 3  is nitro, then R 4  is methoxy; 
     (b) when R 1  is ethyl, R 3  is methyl or methoxy; 
     (c) when R 2  is chloro, R 3  and R 4  are independently C 1  -C 4  haloalkyl, C 1  -C 4  haloalkoxy or C 1  -C 4  alkoxy; 
     (d) when R 2  is methyl or ethyl, R 1  is hydrogen; 
     (e) when R 3  is hydrogen, R 4  is 2-methyl, halo or methoxy; 
     (f) if M is N, R 3  is C 1  -C 4  alkoxy, C 1  -C 4  haloalkyl or C 1  -C 4  haloalkoxy and R 1  is not ethyl; and 
     (g) if R 1  is vinyl, M is N.

FIELD OF THE INVENTION

This invention relates to certain 2-benzoyl pyrrole and benzoylimidazole compounds which demonstrate herbicidal activity.

DESCRIPTION OF THE INVENTION

According to this invention, compounds of the following structure havebeen found to exhibit herbicidal activity: ##STR2## in which R₁ ishydrogen, methyl, ethyl, phenyl, 2-methylphenyl,3-trifluoromethylphenyl, benzyl, 2-methylbenzyl or vinyl;

R₂ is hydrogen, methyl, ethyl or chloro;

R₃ is C₁ -C₄ alkyl, C₁ -C₄ alkoxy, C₁ -C₄ haloalkyl, nitro, p-tolyloxyor p-chlorophenoxy;

R₄ is hydrogen or a methyl, methoxy, trifluoromethoxy or halo group atthe 2, 4- or 5-position;

m is --CH or N; and

X is O or NOR₅ in which R₅ is methyl or ethyl; provided that:

(a) when R₁ is methyl, and

(i) R₃ is methyl, then R₄ is 4-methyl, 4-methoxy or chloro;

(ii) R₃ is nitro, then R₄ is methoxy;

(b) when R₁ is ethyl, R₃ is methyl or methoxy;

(c) when R₂ is chloro, R₃ and R₄ are independently C₁ -C₄ haloalkyl, C₁-C₄ haloalkoxy or C₁ -C₄ alkoxy;

(d) when R₂ is methyl or ethyl, R₁ is hydrogen;

(e) when R₃ is hydrogen, R₄ is 2-methyl, halo or methoxy;

(f) if M is N, R₃ is C₁ -C₄ alkoxy, C₁ -C₄ haloalkyl or C₁ -C₄haloalkoxy and R₁ is not ethyl; and

(g) if R₁ is vinyl, M is N.

Preferably,

R₁ is hydrogen, methyl, phenyl, benzyl or vinyl;

R₂ is hydrogen, methyl or ethyl;

R₃ is methyl, methoxy, ethoxy, isopropoxy, trifluoromethyl,difluoromethoxy, trifluoromethoxy, nitro or p-tolyloxy;

R₄ is hydrogen, 2-methyl, 2-bromo, 4-methyl, 4-methoxy or 4-chloro;

M is --CH or N; and

X is O,

with provisos (a), (b), (d), (e), (f) and (g) above.

As used herein, the term "herbicide" means a compound or compositionwhich adversely controls or modifies the growth of plants. By the term"herbicidally effective amount" is meant any amount of such compound orcomposition which causes an adverse modifying effect upon the growth ofplants. By "plants", is meant germinant seeds, emerging seedlings andestablished vegetation, including roots and above-ground portions. Suchcontrolling or modifying effects include all deviations from naturaldevelopment, such as killing, retardation, defoliation, desiccation,regulation, stunting, tillering, leaf burn, dwarfing, and the like.

The compounds of this invention have been found to be active herbicides,as pre- and/or post-emergent herbicides. Pre-emergence herbicides areapplied prior to emergence of vegetation from the soil; post-emergenceherbicides are applied to control or kill existing vegetation.

Compounds of this invention which are pyrroles may be prepared byreacting a benzoyl chloride or bromide with the appropriate pyrrole.

In general this reaction will produce a mixture of 2- and 3-benzoylpyrroles or imidazoles, and the 2-benzoyl pyrroles or imidazoles of thisinvention are obtained by conventional fractionation. In a few cases thereaction produced only the 2-benzoylpyrrole.

Compounds of this invention which are imidazoles may be prepared byreacting a benzoyl chloride or bromide with the appropriate imidazole inthe presence of n-butyllithium.

The following are examples of the preparation of compounds of thisinvention.

EXAMPLE 1 Preparation of N-benzyl-2-(3'-methylbenzoyl)pyrrole (Compound15 herein)

In a flask were placed 3.0 ml (22.9 mmol) 3-methylbenzoyl chloride and50 ml methylene chloride. Then 22.9 ml (1.0M in CH₂ Cl₂, 22.9 mmol)stannic chloride was added dropwise. The contents of the flask weremixed for 5 minutes, then 3.6 g (22.9 mmol) N-benzylpyrrole in 10 mlmethylene chloride was added dropwise. The reaction mixture was stirredovernight, then quenched with water, washed with brine, dried andcondensed to yield an oil. The oil was purified by flash chromatographywith ethyl acetate/hexanes/silica gel, yielding two fractions. Thesewere analyzed spectroscopically; one was found to be the desired2-benzoyl compound, the other the corresponding 3-benzoyl compound.

EXAMPLE 2 Preparation of 2-(3'-trifluoromethylbenzoyl)pyrrole (Compound7 herein)

In a flask was placed 11.1 ml (74.5 mmol) 3-trifluoromethylbenzoylchloride, dissolved in 50 ml methylene chloride. To this was added 74.5ml (1.0M in CH₂ Cl₂, 74.5 mmol) stannic chloride by syringe. Then, 5.0 g(74.5 mmol) pyrrole was added dropwise. The mixture was stirred for 16hours at room temperature, then quenched with 50 ml water; the resultingmixture was partitioned and the organic layer washed, dried andcondensed, yielding an oil.

The oil was purified by flash chromatography (5% ethyl acetate/hexanes,silica gel), producing two fractions which were submitted forspectroscopic analyses. The first fraction was determined to beunreacted benzoyl chloride; the second was the desired product, m.p.54°-56° C.

EXAMPLE 3 Preparation of 2-(3'-trifluoromethoxybenzoyl)-1-methylimidazole (Compound 35 herein)

In a flask was placed 1.0 g (12.2 mmol) 1-methylimidazole. Then, 5.1 ml(12.8 mmol) n-butyllithium was added dropwise and the mixture wasstirred for 30 minutes. Then, 2.7 g (12.2 mmol)3-trifluoromethoxybenzoyl chloride was added dropwise. The contents weremixed for 2 hours at -78° C., then allowed to warm to room temperaturefor an additional 2 hours. The mixture was quenched with water. Theproduct was extracted with ether, dried and purified by flashchromatography (5-10% ethyl acetate/hexanes, silica gel) and wasidentified as the desired product by spectroscopic analyses.

Table I depicts representative compounds of this invention, prepared bya process as described above. Most compounds were obtained as oils.Structures were confirmed by spectroscopic analyses.

                                      TABLE I    __________________________________________________________________________     ##STR3##    Cmpd.    No. R.sub.1  R.sub.2                    R.sub.3 R.sub.4                                 X    M    __________________________________________________________________________    1   H        H  CH.sub.3                            H    O    CH    2   C.sub.2 H.sub.5                 H  CH.sub.3                            H    O    CH    3   H        C.sub.2 H.sub.5                    CH.sub.3                            H    O    CH    4   C.sub.6 H.sub.5                 H  CH.sub.3                            H    O    CH    5   CH.sub.3 H  CH.sub.3                            4-OCH.sub.3                                 O    CH    6   H        H  CH.sub.3                            5-CH.sub.3                                 O    CH    7   H        H  CF.sub.3                            H    O    CH    8   H        H  CH.sub.3                            H    NOCH.sub.3                                      CH    9   2-(CH.sub.3)C.sub.6 H.sub.4                 H  CH.sub.3                            H    O    CH    10  3-(CF.sub.3)C.sub.6 H.sub.4                 H  CH.sub.3                            H    O    CH    11  CH.sub.3 H  NO.sub.2                            4-OCH.sub.3                                 O    CH    12  CH.sub.3 H  CH.sub.3                            4-CH.sub.3                                 O    CH    13  CH.sub.3 H  CH.sub.3                            4-Cl O    CH    14  H        H  CH.sub.3                            H    NOC.sub.2 H.sub.5                                      CH    15  C.sub.6 H.sub.5 CH.sub.2                 H  CH.sub.3                            H    O    CH    16  H        CH.sub.3                    CH.sub.3                            H    O    CH    17  C.sub.6 H.sub.5                 H  CF.sub.3                            H    O    CH    18  3-(CF.sub.3)C.sub.6 H.sub.4                 H  CF.sub.3                            H    O    CH    19  C.sub.6 H.sub.5 CH.sub.2                 H  CF.sub.3                            H    O    CH    20  C.sub.2 H.sub.5                 H  OCH.sub.3                            H    O    CH    21  2-(CH.sub.3)C.sub.6 H.sub.4 CH.sub.2                 H  CH.sub.3                            H    O    CH    22  C.sub.6 H.sub.5                 H  H       2-OCH.sub.3                                 O    CH    23  H        H  OCH.sub.3                            H    O    CH    24  C.sub.6 H.sub.5                 H  OCH.sub.3                            H    O    CH    25  H        H  OCH.sub.3                            H    O    CH    26  H        H  H       2-CH.sub.3                                 O    CH    27  H        H  H       2-Cl O    CH    28  H        H  H       2-Br O    CH    29  CH.sub.3 H  H       2-CH.sub.3                                 O    CH    30  H        H  H       2-F  O    CH    31  CH.sub.3 H  H       2-Cl O    CH    32  CH.sub.3 H  OCHF.sub.2                            H    O    CH    33  CH.sub.3 Cl OCH.sub.3                            H    O    CH    34  CH.sub.3 H  4-(CH.sub.3)C.sub.6 H.sub.4 O                            H    O    CH    35  CH.sub.3 H  OCF.sub.3                            H    O    N    36  CHCH.sub.2                 H  OCF.sub.3                            H    O    N    37  CH.sub.3 H  4-ClC.sub.6 H.sub.4 O                            H    O    CH    __________________________________________________________________________

HERBICIDAL ACTIVITY TESTS

Compounds of Table I were tested for herbicidal activity as follows:

PRE-EMERGENCE HERBICIDAL EVALUATION

On the day preceding treatment, seeds of several different weed specieswere planted in a sandy loam soil containing only trace organic matter.Propagules were sown in individual rows using one species per row acrossthe width of a flat. The grass weeds planted were green foxtail (Setariaviridis), wild oat (Avena fatua) and barnyardgrass (Echinochloacrus-galli). Broadleaf weeds utilized were wild mustard (Brassicakaber), velvetleaf (Abutilon theophrasti), and annual morningglory(Ipomoea spp.). Additionally, yellow nutsedge (Cyperus esculentus)nutlets were sown. Seeding depths ranged from 1.0 to 1.5 cm and plantdensities ranged from 3 to 25 plants per row depending on individualplant species.

Solutions of the test compounds were prepared by weighing out 74.7 mg ofthe test compound into a bottle, then dissolving the compound in 7 ml ofacetone containing 1% v/v Tween 20 (polyoxyethylene sorbitan monolaurateemulsifier) as a surfactant and then adding 7 ml of deionized water toreach a 14 ml final volume. Tween 20 content was 0.5% v/v of the finalspray volume. Additional solvents, not exceeding 2 ml (15% of sprayvolume), were used if needed to dissolve the compound.

The soil surface was sprayed inside an enclosed linear spray table withthe nozzle set at 30.5 cm (12 inches) above the soil line. The spraytable was calibrated to deliver 748 L/ha (80 gal/A) with the applicationrate being 4 kg/ha. After treatment the flats were placed into agreenhouse and watered overhead by sprinkling. The greenhouseenvironmental systems provided the plants with natural and artificial(via metal halide lamps) lighting to attain 14 hours of light per day.Day and night temperatures were maintained at 29° and 21° C.respectively.

The degree of weed control was evaluated and recorded 7-21 days aftertreatment as a percentage of weed control as compared to the growth ofthe same species of the same age in an untreated control flat. Percentcontrol is the total injury to the plants due to all factors includinginhibited emergence, stunting, malformation, chlorosis and other typesof plant injury. The control ratings range from 0 to 100 percent, where0% represents no effect with growth equal to the untreated control andwhere 100% represents complete kill. A dash indicates that no test wasperformed at that level of application.

POST-EMERGENCE HERBICIDAL EVALUATION

The soil was prepared and seeded with the same species and methodologydescribed for the pre-emergence test. Post-emergence flats were placedin the greenhouse under the same environmental conditions as describedfor the pre-emergence flats and watered overhead by sprinkling. Plantswere grown for 10 to 12 days (or to the appropriate growth stage) priorto compound application. Grasses were sprayed at a 3 to 4 leaf stage andbroadleaves at a 1 to 2 leaf stage. Yellow nutsedge was 5 to 7 cm tallat application.

Plants were sprayed 30.5 cm (12 inches) above the foliage with the samespray solution as prepared for the pre-emergence test. The applicationrate was 4 kg/ha. Treated plants were then returned to a greenhouse andwatered daily without wetting the foliage. The degree of weed controlwas evaluated 17 to 21 days after application and recorded as percentageof control as compared to the growth of the sane species in an untreatedcontrol flat of the same age. The percent control scale (0-100%) used toevaluate the pre-emergence treatment was also applied to thepost-emergence treatment.

Results are listed in Table II below, expressed as average control ofthe three grasses (GR) (wild oat, watergrass, foxtail) and threebroadleaf weeds (BL) (morningglory, mustard, velvetleaf), and ofnutsedge (NS).

                  TABLE II    ______________________________________    Com-  % Control, 3.57 kg/ha    pound Pre-emergence    Post-emergence    No.   GR avg.  BL avg.  NS   GR avg.                                        BL avg.                                               NS    ______________________________________     1    46       46       0    5      36     5     2    40       28       0    3       5     5     3    73       53       5    18     63     5     4    61       60       10   23     85     5     5    81       28       10   11     30     0     6    16       41       10   10     38     0     7    20       33       0    3      11     5     8    18       35       0    13     43     0     9     6       30       0    6      46     0    10    26        6       0    6      50     0    11    63       10       0    28     10     5    12    48       13       0    6       8     0    13    67       21       0    5      16     5    14    48       51       0    5      33     5    15    76       58       0    6      51     5    16    68       73       15   23     23     10    17     5       18       0    5      53     0    18    10       20       6    8      36     5    19     5       26       0    5      35     0    20    35       33       0    3      15     5    21     3        5       0    15     43     0    22    38       61       10   15     38     0    23    40       43       0    6      21     0    24    16       70       0    6      61     0    25     5       13       0    5      66     0    26     3       36       0    3      18     0    27     0       33       0    3      25     0    28     3       56       5    1      18     0    29    56       65       40   1       8     0    30     3        5       0    1      33     0    31     6       33       0    3       6     0    32    63       38       0    5      21     5    33    65       33       0    8      10     0    34    55       68       0    13     50     10    35    41        3       0    6      20     5    36    58       58       5    8      10     5    37     0        1       --   3      31     5    ______________________________________

In practice, a pure compound can be used as an herbicide. However, ingeneral, the compounds are first formulated with one or more inertcarriers or diluents suitable for herbicidal use, before being applied.

The compositions or formulations, including a compound as describedherein, may exist in any one of a number of solid or liquid forms.Examples of liquid forms are emulsifiable concentrates, flowables andpastes. Such compositions may contain, in addition to the activecompound or compounds, various carriers or diluents; surface activeagents (wetting agents, dispersing agents and/or emulsifying agents);solvents (water, or organic solvents such as aromatic solvents orchlorinated aliphatic solvents); adhesives; thickeners; binders;antifoaming agents; and other substances as mentioned herein. Solidcarriers or diluents included in such compositions or formulations mayinclude, for example, ground natural minerals such as kaolins, alumina,calcium carbonate, silica, kieselguhr, clay, etc.; ground syntheticminerals such as various silicates and aluminosilicates and groundvegetable products such as bark, cornmeal, sawdust, cellulose powder andthe like.

To manufacture solid compositions, the active substances are mixed withsolid carriers or diluents such as those mentioned above and the mixtureis ground to the appropriate size. Granules can be manufactured bydissolving an active compound in an organic solvent and applying themixture, for example, by atomization, onto an absorptive granulatedinert material, such as silica. Adhesives may be utilized to assist inthe incorporation of the compound onto the solid particles. Pellets orgranules can be manufactured by extrusion with appropriate carriers andbinders.

Wettable powders, flowables, and pastes are obtained by mixing andgrinding an active compound with one or more dispersing agents and/orsolid carriers or diluents. Also included may be wetting agents and/ordispersing agents, for example, lignins, methyl cellulose,naphthalenesulfonic acid derivatives, fatty alcohol sulfates and varioustypes of alkali and alkaline earth metal salts of fatty acids.

Emulsifiable concentrates are generally obtained by dissolving theactive compound in an organic solvent, for example, butanol,cyclohexanone, xylenes, or higher boiling aromatic hydrocarbons. Toobtain suspensions or emulsions in water, wetting agents are generallyalso added.

The compositions may also be used in the form of microcapsules.Microcapsules consist of fully enclosed or encapsulated droplets orgranules containing the active compound, enclosed within an inert porousmembrane, so as to permit escape of the encapsulated material into thesurrounding medium or environment at a controlled rate.

Useful encapsulating materials include natural and synthetic rubbers orlatexes, cellulosic materials, styrenebutadiene copolymers,polyacrylonitriles, polyacrylates, polyesters, polyamides, polyurethanesand starch xanthates.

It is possible to use highly concentrated liquid compositions containingup to about 95% by weight of the active compound, or even the activecompound alone for those compounds which are liquids, when applying thecompound in the form of a finely divided liquid by use of variousatomizing equipment, for example by airplane crop-spraying techniques.For other purposes, however, the various types of compositions which canbe utilized for these compounds will contain varying amounts of thecompound according to the type of composition and the intended use.

In general, compositions may contain from 0.1 to 95% of the activecompound, more preferably from 0.5 to 90%. Some typical compositionswill contain an active compound as follows: Wettable powders, flowablesand pastes-20 to 90% active compound; oil suspensions, emulsions,solutions and emulsifiable concentrates-5 to 90% active compound;aqueous suspensions-10 to 50% active compound; dusts and powders-1 to25% active compound; granules and pellets-1 to 20% active compound.

The rate of application of the active compound to a locus to becontrolled will depend on the activity of the compound and/orcomposition and the nature of the seeds and plants to be controlled andwill vary from about 0.05 to about 50 pounds per acre (about 0.06 toabout 56 kg/ha).

Compositions containing one or more of the active compounds described,in a herbicidally effective amount, may be applied to the plant or locusto be controlled in any conventional manner. Thus, powders and variousliquid compositions containing the active compound can be applied by theuse of power dusters, boom and hand sprayers and spray spray dusters, orapplied from airplanes as mists or sprays. When applied in the lattermethod, they may be effective in very low dosages. To modify or controlgrowth of germinating seeds or emerging seedlings, liquid compositionsmay be applied to the soil with conventional methods and may bedistributed in the soil to a depth of one-half inch below the soilsurface. The compositions need not be admixed with the soil particles,but can be applied merely by sprinkling on the surface of the soil.

Compositions including active compounds may also be applied by additionto irrigation waters supplied to the field to be treated. This method ofapplication permits penetration of the compounds into the soil as thewater is absorbed therein.

EXAMPLES OF TYPICAL COMPOSITIONS

    ______________________________________    EXAMPLES OF TYPICAL COMPOSITIONS    Ingredient            Weight %    ______________________________________    Oil    Active Compound        1    Oil solvent-heavy aromatic naphtha                          99    Total                 100    Emulsifiable Concentrate    Active Compound       50    Kerosene              45    Emulsifying agent (mixture of long                           5    chain ethoxylated polyethers with    long chain sulfonate)    Total                 100    Emulsifiable Concentrate    Active Compound       90    Kerosene               5    Emulsifying agent (mixture of long                           5    chain ethoxylated polyethers with    long chain sulfonate)    Total                 100    ______________________________________    Dusts and/or Powders    Ingredient        Wt. %    Wt. %    Wt. %    ______________________________________    Active Compound   0.5      50.0     90.0    Attapulgite Clay Powder                      93.5     44.0     4.0    Sodium lignin sulfonate                      5.0      5.0      5.0    Sodium dioctyl sulfosuccinate                      1.0      1.0      1.0    TOTAL             100.0    100.0    100.0    ______________________________________

The compositions of the invention may comprise, in addition to one ormore compounds of the invention, one or more compounds not of theinvention but which possess biological activity. Compounds not of thisinvention may be other pesticidal agents, such as herbicides,fungicides, insecticides, acaricides, nematocides, bactericides, andplant growth regulators. Such compositions may also contain soildisinfectants or fumigants and may further contain fertilizers, thusmaking it possible to provide multi-purpose compositions containing oneor more of the compounds described herein as well as, optionally, otherpesticides and also fertilizers, all intended and formulated for use atthe same locus. Accordingly, in yet a still further embodiment, theinvention provides an herbicidal composition comprising a mixture of atleast one herbicidal compound of formula (I) as hereinbefore definedwith at least one other herbicide.

The other herbicide may be any herbicide not having the formula (I). Itwill generally be an herbicide having a complementary action in theparticular application.

Examples of useful complementary herbicides include:

A. Benzo-2,1,3-thiodiazin-4-one-2,2-dioxides such as bentazone;

B. hormone herbicides, particularly the phenoxy alkanoic acids such asMCPA, MCPA-thioethyl, dichlorprop, 2,4,5-T, MCPB, 2,4-D, 2,4-DB,mecoprop, trichlopyr, fluroxypyr, clopyralid, and their derivatives(e.g. salts, esters and amides);

C. 1,3-dimethylpyrazole derivatives such as pyrazoxyfen, pyrazolate andbenzofenap;

D. Dinitrophenols and their derivatives (e.g. acetates such as DNOC,dinoterb, dinoseb and its ester, dinoseb acetate;

E. dinitroaniline herbicides such as dinitramine, trifluralin,ethalfluralin, pendimethalin; and oryzalin;

F. arylurea herbicides such as diuron, flumeturon, metoxuron, neburon,isoproturon, chlorotoluron, chloroxuron, linuron, monolinuron,chlorobromuron, daimuron, and methabenzthiazuron;

G. phenylcarbamoyloxyphenylcarbamates such as phenmedipham anddesmedipham;

H. 2-phenylpyridazin-3-ones such as chloridazon, and norflurazon;

I. uracil herbicides such as lenacil, bromacil and terbacil;

J. triazine herbicides such as atrazine, simazine, aziprotryne,cyanazine, prometryn, dimethametryn, simetryne, and terbutryn;

K. phosphorothioate herbicides such as piperophos, bensulide, andbutamifos;

L. thiolcarbamate herbicides such as cycloate, vernolate, molinate,thiobencarb, butylate*, EPTC*, triallate, diallate, ethyl esprocarb,tiocarbazil, pyridate, and dimepiperate;

M. 1,2,4-triazin-5-one herbicides such as metamitron and metribuzin;

N. benzoic acid herbicides such as 2,3,6-TBA, dicamba and chloramben;

O. anilide herbicides such as pretilachlor, butachlor, the correspondingalachlor, the corresponding compound propachlor, propanil, metazachlor,metolachlor, acetochlor, and dimethachlor;

P. dihalobenzonitrile herbicides such as dichlobenil, bromoxynil andioxynil;

Q. haloalkanoic herbicides such as dalapon, TCA and salts thereof;

R. diphenylether herbicides such as lactofen, fluroglycofen or salts oresters thereof, nitrofen, bifenox, acifluorfen and salts and estersthereof, oxyfluorfen and fomesafen; chlornitrofen and chlomethoxyfen;

S. phenoxyphenoxypropionate herbicides such as diclofop and estersthereof such as the methyl ester, fluazifop and esters thereof,haloxyfop and esters thereof, quizalofop and esters thereof andfenoxaprop and esters thereof such as the ethyl ester;

T. cyclohexanedione herbicides such as alloxydim and salts thereof,sethoxydim, cycloxydim, tralkoxydim, and clethodim;

U. sulfonyl urea herbicides such as chlorosulfuron, sulfometuron,metsulfuron and esters thereof; benzsulfuron and esters thereof such asthe ester thereof methyl, DPX-M6313, chlorimuron and esters such as theethyl ester thereof, pirimisulfuron and esters such as the methyl esterthereof, DPXLS300 and pyrazosulfuron;

V. imidazolidinone herbicides such as imazaquin, imazamethabenz,imazapyr and isopropylammonium salts thereof, imazethapyr;

W. arylanilide herbicides such as flamprop and esters thereof,benzoylprop-ethyl, diflufenican;

X. amino acid herbicides such as glyphosate and gluyfosinate and theirsalts and esters, sulphosate, and bilanafos;

Y. organoarsenical herbicides such as MSMA;

Z. herbicidal amide derivative such as napropamide, propyzamide,carbetamide, tebutam, bromobutide, isoxaben, naproanilide, diphenamid,and naptalam;

AA. miscellaneous herbicides including ethofumesate, cinmethylin,difenzoquat and salts thereof such as the methyl sulfate salt,clomazone, oxadiazon, bromofenoxim, barban, tridiphane, (in the ratio3:1) flurochloridone, quinchlorac and mefanacet;

BB. examples of useful contact herbicides include bipyridyliumherbicides such as those in which the active entity is paraquat andthose in which the active entity is diquat.

* These compounds are preferably employed in combination with a safenersuch as 2,2-dichloro-N,N-di-2-propenylacetamide (dichlormid).

What is claimed is:
 1. A method of controlling undesirable vegetationcomprising applying to said vegetation or the locus thereof aherbicidally effective amount of a compound having the formula ##STR4##in which R₁ is hydrogen, methyl or ethyl;R₂ is hydrogen, methyl orethyl; R₃ is C₁ -C₄ alkyl, C₁ -C₄ alkoxy, C₁ -C₄ haloalkyl or nitro; R₄is hydrogen or a methyl, methoxy, or trifiuoromethoxy group at the 2- 4-or 5-position; provided that:(a) when R₁ is methyl, and (i) R₃ ismethyl, then R₄ is 4-methyl or 4-methoxy; (ii) R₃ is nitro, then R₄ ismethoxy; (b) when R₁ is ethyl, R₃ is methyl or methoxy; (c) when R₂ ismethyl or ethyl, R₁ is hydrogen; (d) if R₁, R₂ and R₄ are hydrogen, thenR₃ is not methoxy; and (e) if R₁ is methyl, R₂ and R₄ are hydrogen, thenR₃ is not CF₃.
 2. A method according to claim 1 in which R₂ is hydrogen.3. A method according to claim 1 in which R₂ is methyl or ethyl and R₁is hydrogen.
 4. A method according to claim 1 in which R₃ is methyl andR₄ is hydrogen.
 5. A method according to claim 4 in which R₂ is methyl.6. A method according to claim 4 in which R₂ is ethyl.
 7. A methodaccording to claim 1 in which R₁ is methyl, and R₂ is hydrogen.
 8. Amethod according to claim 7 in which R₃ is methyl and R₄ is 4-methoxy.9. A method according to claim 7 in which R₃ is nitro and R₄ is4-methoxy.
 10. A herbicidal composition comprising from about 0.5 toabout 95% by weight of a compound having the formula: ##STR5## in whichR₁ is hydrogen, methyl or ethyl;R₂ is hydrogen, methyl or ethyl; R₃ isC₁ -C₄ alkyl, C₁ -C₄ alkoxy, C₁ -C₄ haloalkyl or nitro; R₄ is hydrogenor a methyl, methoxy, or trifluoromethoxy group at the 2- 4- or5-position; provided that:(a) when R₁ is methyl, and (i) R₃ is methyl,then R₄ is 4-methyl or 4-methoxy; (ii) R₃ is nitro, then R₄ is methoxy;(b) when R₁ is ethyl, R₃ is methyl or methoxy; (c) when R₂ is methyl orethyl, R₁ is hydrogen; (d) if R₁, R₂ and R₄ are hydrogen, then R₃ is notmethoxy; and (e) if R₁ is methyl, R₂ and R₄ are hydrogen, then R₃ is notCF₃ ; and a diluent or carrier suitable for use with herbicides.